Method of tungsten inert gas welding electronic components and burning away contaminants

ABSTRACT

A method and apparatus wherein linear metallic elements such as copper wire leads are welded to workpieces, such as terminal lugs of electrical and electronic components. An electric arc welding method is used to produce an electrical or electronic component with copper wire leads rigidly and reliably attached, without requiring prior cleaning of the terminal lugs of the component. In the welding step a surplus of heat energy greater than that necessary to melt and coalesce the weld material is applied to the welding zone in order to burn away contaminents at the area to be welded.

Chan'owitz [451 Mar. 5, 1974 [73] Assignee: Pico-Matic, Inc-., Chicago,Ill.

Primary ExaminerJ. V. Truhe [22] Flled: June 1972 AssistantExaminerGeorge A. Montanye [2]] Appl. No.: 259,841

Related US. Application Data [57] ABSTRACT [63.] Continuafio 114mm ofSen No 115,177, Feb 16 A method and apparatus wherem llnear metalhc ele-1971, abandoned, ments such as copper wire leads are welded toworkpieces, such as terminal lugs of electrical and elec- 52 us. c1219/137, 29/628, 219/121, troni components An electric arc Weldingmethod is 1 3 used to produce an electrical or electronic component 511111. c1; B23k 9/00 with pp Wire leads rigidly and reliably attached,[58] Field of Search 219/131, 137, 121, 127, 75; Without requiring Priorcleaning of the terminal lugs of 338/329, 332, 266; 29/628, 630 G thecomponent. In the welding'step a' surplus of heat energy greater thanthat necessary to melt and co- 5 Reisrences Cited ,alesce the weldmaterial is applied to the welding zone UNITED STATES PATENTS in ordertoburn away contaminents at the area to be l d. 1,605,860 11/1926 Snelling219/137 we de 903,860 11/1908 Howell 219/121 6 Claims, 8 Drawing Figures3O zfi 24 v Electrode 32 W Id 1 34 26 y e we 16 18 M och 1 me @9111?- 142oi L I 17 i" l 21 IO 23 v I 82 2 8 22 l METHOD OF TUNGSTEN INERT GASWELDING ELECTRONIC COMPONENTS AND BURNING AWAY CONTAMINANTS Inventor:Harry Chanowitz, Skokie, Ill.

3,634,649 ll/l972 Rager, ..2l9/l37 OTHER PUBLICATIONS InternationalElectronic Circuit Packaging Sympo sium, M. J. Davis, 8/69, pp. l-7. 1

PATENHW 3.795.786

SHE] 1 BF 2 FIG. 1

FIG. 2

Pmmznm 3.795.786

SHEET 2 OF 2 FIG, 4 FIG, 5

METHOD OF TUNGSTEN INERT GAS WELDING ELECTRONIC COMPONENTS AND BURNINGAWAY CONTAMINANTS BACKGROUND OF THE INVENTION This application is acontinuation-in-part of copending application Ser. No. ll5,l77 filedFeb. 16, 1971 now abandoned.

This invention relates generally to bonding, and more particularly, tothe use of a novel welding process to lytic copper, and workpieces suchas the terminal lug's of electrical and electronic components. Theunique welding method which forms a part of my invention may also beused to bond heretofore non-weldable or difficultly welded elements ofvarious types.

In the manufacture and use of electrical and electronic equipment, theconduction and flow of electric energy from one component to another isaccomplished by the use of conductor leads connected to the components.For various reasons, of which efficiency of electrical conductivity andeconomy of production are primary, copper has been accepted by theelectrical/electronic industry as the standard for a conductor. ltisalso acknowledged by the electrical/electronic industry that a weldedconnection between conductor leads and electric components is bothelectrically and metallurgically more sound, as contrasted to solderedor mechanical connections, or combinations thereof.

oxidation, and so on until the component fails or burns out.

Soldered connections provide a more stable bond electrically. However,the bond produced is not as mechanically strong as a welded bond, due tothe absence of intergranular dipersion between one metal and another(coalescence) in a soldered bond. A soldered connection is limited inmechanical strength by the ultimate strength of the solder, which isless than that of the raw material of the elements being joined.Also,'as in mechanical lead-component connections, the surfaces to besoldered must be cleaned and fluxed prior to bonding. A mechanicalattachment usually supplements a solder joint in order to give the bondadditional strength. This naturally results in increased cost and size.

A welded connection, on the other hand, provides a mechanically,electrically and metallurgically superior bond which, when using the arcwelding process of the present invention, does not require the priorstep of cleaning or fluxing parts. Also, a welded joint derives itsstrength from the ultimate stress of the base metals or of the weldalloy, which stress point is considerably higher than that of solder.

produce a bond between linear metallic elements such as wire conductorleads composed of pure or' electro the electrodes produces heat in thejoint due to the re- 7 Despite the desirability of a welded pure orelectrolytic copper connection, no high quality and economicallyfeasible electrical or electronic components manufactured in this mannerare available on todays market. While the most desirable material fromwhich to fabricate a lead wire is copper, pureor electrolytic coppercannot be readily welded to terminal lugs of electrical components bymethods known to the prior art. As a consequence, manufacturers whosupply electrical or electronic components with welded leads haveresorted to using a copper alloy, such as six per cent nickel (nominalanalysis), as a lead material. Others use copper-clad, iron core leadwires in producing welded lead components. In those few instances wherecopper leads are attached to components by welding, the joint is usuallyof inferior mechanical quality due to the resistance welding methodused, or other problems and the configuration as to how the wire isattached is restricted by todays art.

The process most frequently employed at present is to weld one part toanother in the fabrication of electrical and electronic components isknow as resistance welding. This encompasses several methods whereincoalescence of the interface between surfaces to be welded is producedby he heat generated by the resistance of the work to the flow ofelectric current in a circuit of which the work isa part. The resistancewelding process is also accompanied by the publication of pressure tothe bonded junction. Included among the resistance welding method arespot, flash, upset and percussion welding.

Resistance spot welding is applied to a lap joint of.

two mating workpieces wherein coalescence occurs at a spot on the matingsurfaces directly beneath where the surfaces are held together underpressure applied by two electrodes. Electric current passing betweensistivity of the material to be welded, and contact resistance of thematerials, and this heat causes the surfaces to be welded together. Theelectrode material is usually a high copper bearing alloy, or else ahigh tungsten alloy. Copper or copper bearing alloys are used due totheir low electrical resistivity and high heat conductivity, which keepsthe heat generatedat the electrodernaterial interface to a minimum toprevent the electrodes from becoming fused or stuckto the materials. Forthese same reasons, it is quite difficult to produce a spot welded jointif one of the materials to be welded is copper.

Tungsten or tungsten-bearing alloys have been used as electrodes withlimited success in the resistance spot welding of copper. The relativelyhigh electrical resistivity of the tungsten electrode and its low heatconductivity aid in generating heat for the welding of copper by actingas a heat source rather than as'a heat sink. Sticking does not occur atthe copper-tungsten interface because of the extremely high meltingpoint'of tungsten (approximately '6,400F.). However, theheat balancethat must be maintained is critical, and consequently the process ismarginal. In fact, this process is siderably reduced. Accordingly, theresistance spot welding of copper wire is almost always accompanied bysome means of mechanical attachment of the copper wire to the terminalin order to protect the welded joint from mechanical stress.

Copper wires have also been welded successfully by the flashand upsetresistance welding processes. Coalescence is produced over the entirearea of abutting surfaces by the heat obtained from resistance to theflow of electric current between the two surfaces. In flash welding,pressure is applied after heating is substantially completed. Upsetwelding is accomplished by applying pressure before heating andmaintaining the pressure during the heating period. In each process thecopper wire is held in a clamping electrode which is placed at somedistance from the weld junction. Electric current passes through thewire and the junction, generating heat for the weld. The amount of heatdeveloped is a function of the length of wire extending beyond theclamp. By varying this length, the proper amount of heat can bedeveloped by the electric current passing through the wire.

The flash and upset resistance welding processes are limited to use withsolid wire rather than braided or stranded wire. The latter wires aretoo flexible to withstand the compressive stress resulting from theapplication of pressure required to keep the wire in contact with thebase surface. Further, the flash and upset processes imposeconfiguration limitations due to the fact that the wire must be normalto the base surface. Also, critical to the quality of the weld formed bythese methods is the cleanliness of the surfaces to be welded. Thisnecessitates the extra step of cleaning the surfaces prior to welding, astep which is eliminated in the welding procedure which is the subjectof the present invention.

The welding of copper wires to base elements has also previously beenperformed by percussion welding, which is a resistance welding process.The wire and base element are connected to suitable arc weldingapparatus such that the wire and base both form part of the electricalcircuit of the welding apparatus. An arc is struck between the wire andbase, with force percussively applied during or immediately followingthe electrical discharge. Coalescence results at the point of abutmentby the heat obtained from the are, which is produced by the rapiddischarge of electrical energy,

and is extinguished by pressure percussively applied by urging theelectrode (wire) toward the junction during discharge. The configurationof the joint is abutt weld, similar to that obtained in flash or upsetwelding, but differs from those processes in the use of an electricalarc to produce the weld.

Percussive welds are less vulnerable than flash or upset welds to theeffects of contaminated surfaces. However, the pressure applied to theelectrode in percussion welding results in considerable spewing andexpulsion of molten metal. A, further disadvantage of adaptingpercussion welding techniques to the fabrication of electrical andelectronic components with copper wire leads attached is that an arcmust be drawn from the terminal to the wire, which requires anelectrical connection to be made to the terminal. This, plus the factthat pressure must constantly be applied to the junction, means that anappreciable amount of terminal lug must be present upon which to attachthe wire. Most electrical components are relatively small in size,

and the terminal lugs of these components are not large enough toproduce good percussive welded joints.

The above described processes have previously been used to weld leadwires to electrical components, and generally to weld copper. However,when an effort is made to use these processes to weld copper wire leadsto electric and electronic components, several design limitations havethwarted the success of these efforts. The small size of a terminal lug,its composition, and the configuration of the joint have, prior to myinvention, been factors in forcing design engineers to find alternatemeans of attaching copper leads to electrical and electronic components.Also, in using these known processes, the surfaces to be welded must beimmaculately or reasonably clean prior to welding, the degree ofcleanliness depending upon the process used. The surfaces to be weldedmust also be accessible to welding electrodes for the conduction ofcurrent during welding, and be able to be attached to a source ofpressure. Because of these limitations, copper substitutes or alloyedcopper are used in the vast majority of commercially availableelectrical components comprising a welded lead wire attached to theterminals.

Having thus described the state of the art, of which the presentinvention represents a significant step forward, it is a principalobject of my invention to provide a method of attaching a copper wirelead to a workpiece, such as the terminal lug of an electrical orelectronic component, which method circumvents the limitationsencountered in the known resistance welding methods.

It is a further object of the present invention to provide a procedurefor affixing copper wire leads to the terminals of electrical andelectronic components by the process of electric arc welding, whereinthe electric arc produces coalescence between the copper wire lead andthe terminal. Another object is to provide a method of welding copperwire leads to the terminals of electrical and electronic components,which method avoids the step of cleaning the terminals prior toattaching the lead wire. It has been discovered that a copper lead wiremay be firmly welded to a terminal lug through heavy oxide and othercontaminants which have to be removed when soldering.

An additional object of the present invention is to provide anelectrical or electronic component with copper wire leads are welded tothe terminals of the component.

Another object of my invention is to produce an electrical or electroniccomponent which is not limited in temperature applications to thesoftening point of solder.

Another object of the present invention is to provide a novel weldingprocedure for attaching linear metallic elements to workpieces.

A further object of the present invention is to provide an apparatus forwelding copper'leads to terminals of electrical components by utilizingan electric arc in an inert gas atmosphere to produce coalescencebetween the lead and the terminal.

Other objects and advantages of my invention will become apparent fromthe description of the invention in the following specification.

To fully understand the invention, reference should be made to theaccompanying drawing, forming part of thespecification, in which:

FIG. 1 is a diagrammatic illustration of the apparatus necessary tocarry out the method of an embodiment of the present invention, showingan electrical component with a wire lead in the process of being weldedto one terminal lug of the component, and a finished, attached wire leadon the other terminal;

FIG. 2 is a general assembly view of a welding apparatus constructed inaccordance with the present invention',

FIGS. 3, 4 and '5 are illustrations of alternate procedures for locatinga copper wire lead relative to the terminal lug of an electrical orelectronic component in accordance with the present invention;

FIG. 6 is a detail view of a copper wire lead properly attached to theterminal lug of an electrical or electronic component in accordance withthe preferred method forming an embodiment of the present invention;

FIG. 7 is a detail view of a wire lead improperly attached to theterminal lug of an electrical or electronic component, illustrating theresult achieved by not following the principles embodied in the presentinvention; and

FIG. 8 is a sectional view taken along line 88 in FIG. 1 illustratingthe manner in which the electrical component is positioned for welding.

While the drawing shows the preferred forms of my invention, it shouldbe understood that various changes, or modifications, may be made withinthe scope of the appended claims without departing from the spirit of myinvention.

DESCRIPTION OF THE INVENTION The present invention relates to theelectric arc welding of wire leads, preferably of copper, to workpiecessuch as terminal elements or lugs of electrical and electroniccomponents. In particular, an inert gas tungstenarc welding procedure isemployed wherein coalescence between the copper wire lead and theterminal is produced by heating the junction of the wire with anelectric arc formed between the terminus portion of the copper wire anda non-consumable, tungsten tip forming part of a welding electrode. Theare is shielded by an atmosphere of inert gas, such as argon, formedaround the junction and the are. In the trade, this welding process iscommonly known as TIG welding (Tungsten Inert Gas).

Specifically, I will describe my invention as applied to the attachmentof solid, stranded or braided copper wires to the terminals of vitreousenameled resistors. It is to be understood, however, that my inventionmay be utilized to attach copper or'other metallicwire leads toterminals of other components, such as transistors and othersemi-conductor elements, capacitors, ceramic crystals and the like.

A resistor of the type aforementioned is designated in FIG. 1 by thenumeral 10, and comprises a ceramic tube or core having a wound wireelement surrounding the core. At either end of the resistor 10, terminalelements or lugs l2, 14 are suitably attached to the core of theresistor 10. The wound wire element is covered with a baked vitreousenamel coating which forms the outer insulating surface of the resistor10. Each termi nal lug 12 and 14 is connected to one end of the wirewrapped around the core, completing an electrical path from lug 12 tolug 14 through the resistor 10. In most commercially availableresistors, the terminal lugs I2 and 14 are formed from a stainless steelor nickel-' iron band, approximately /s inch wide by 0.020 inches thick,and extend radially from the core to an extent of about Vs inch abovethe enamel covering. The melting temperature of the terminal lug isapproximately 2,200 T f which is higher than the melting temperature ofc0pper(1.980 F.).

The entire resistor I0 is coated with vitreous enamel, except for theoutermost edge of each terminal lug l2 and 14. However, in the processof manufacturing the resistor, which is described in my earlier US. Pat.Nos. 2,460,807 and 2,479,556, the vitreous enameling operation takesplace in an oxidizing atmosphere at a relatively high temperature,resulting in the formation of a heavy oxide film on the terminalelements 12 and 14. The presence of this oxide film and enamel film isordinarily an impediment to forming a weld with the terminal lugs 12 and14 but, as will be described in more detail, this film does not impairthe operation, or adv versely effect the result'of the presentinvention.

The. wire leads 16 and 18, which are to be attached to the terminal'lugs12 and 14 may be tinned copper wire, either solid or braided, usually0.040 inch in diameter. The wire is tinned primarily due to customerrequirements -i.e.: the ends of the wires 16 and 18, which are notattached to the terminal lugs 12 and 14, are prevented from oxidizingand these ends are easily soldered if tinned prior to welding. Thetinning of the wires does not affect nor impede the welding process usedin accordance with the present invention.

As seen in FIG. I, the copper wires 16 and 18, are held by clamps 20 and22, longitudinally to the body of resistor 10, and in abutment with theupper edge of the terminal lugs 12 and 14 as will be detailed withreference to FIG. 8. Clamps 20 and 22 are electrically connected toground through wires 21 and 23, respectively. The terminus-portion 17 ofeach wire 16 and 18 projects beyond the inner vertical edges of theterminal lug it contacts by approximately Vs inch. As will be explainedin detail, the extension of the wire a short distance beyond the edge ofthe terminal lug is an important feature in the efficacious performanceof the preferred embodiment of the present invention.

Located just beyond and above the junction point of the terminal lug 12and wire 16, as seen in FIG. I, is a welding electrode 25 having avnon-consumable tungsten tip 26. A shield of inert gas 28 is emitted fromthe end of electrode 24, and surrounds the tungsten tip 26, the junctionbetween wire 16 and terminal lug 12, and extending portion 17 of wire16. A service line 30 connects electrode 24 to an electric arc welding"machine 32 and a supply of inert gas 34 such as argon,-which isfurnished to arc welding machine 32 through tube 36. Service line 30transmits the inert gas to the lowermost portion of electrode 24, whereit is dispersed. Service line 30 also carries a supply of electricalenergy to tungsten tip 26 for the purpose of striking an electric arc,between tip 26 and terminus portion 17 of wire 16. Inert gas is alsosupplied to the inert gasshield 28 by conduit 82. The conduit 82 ispreferably inclined upward slightly from a horizontal plane and receivesinert gas from the supply of inert gas 34.

A typical arc welding machine, when regulated for TIG welding of wireshaving a diameter of approximately 0.040 inch produces a ten amperecurrent at 1 2 volts D.C.-to maintain the arc. An initial charge ofvolts is supplied to strike the arc. Depending upon the application andthe different size wires to be used in practicing the present invention,the above current and voltage parameters may vary.

Welding of the wire 16 to the terminal lug 12 is accomplished bylocating the tungsten tip 26 of electrode 24 at a point midway along theterminus portion 17 of wire 16, and H32 inch above the wire. Weldingmachine 32 is started and an electric arc is struck between the tungstentip 26 and copper wire 16. The electric current is carried through thewire 16 and clamp through wire 21 to ground. A shield 28 of argonsurrounds the tungsten tip 26 and the work to be joined. The are createsa heat which melts the terminus portion 17 of copper wire 16. As thewire melts, it forms a ball of molten metal 38 (FIG. 6) due to surfacetension, which ball 38 travels along the terminus portion 17 of wire 16toward the the terminus lug 12. The are is extinguished after a timelapse of approximately /2 to 3 seconds, and the molten ball of wirecoalesces with terminal lug 12.

The configuration of the final welded junction is illustrated in FIG. 6.During the welding process, the arc follows the ball of molten metal 38until it reaches the terminal 12, at which time the terminal is heatedby the are as well as the ball of molten metal 38. The are travels overa lateral distance of only approximately l/l6 inch, and as a result, nomovement of the tungsten tip 26 is necessary during the welding processin order to enable the arc to follow the ball of molten metal.

During the welding of the lead wire 16 an amount of heat energy isapplied to the welding zone which is greater than the heat energynecessary to melt the wire 16 and form the molten ball of metal 38. Theexcess heat energy generated by the welding are permits contaminants inthe welding zone to be burned away and allows for variation in thelength of the end portion 17 of the lead wire. For example, if a largerthan normal amount of the lead wire 16 extends beyond the terminal lug12, the additional portion of the lead wire will also be melted and formpart of the ball of molten metal 38 due to the excess heat energysupplied by the welding arc. The welding arc can typically be maintainedfor a period twice as long as the period necessary to melt an ordinarylength of the lead wire 16 and thus provide twice the heat energynecessary to form the weldment. The excess energy generated in thewelding process is carried away by the clamp 20 which serves'as a heatsink for the lead wire 16 and the terminal lug 12. Also, the clamp 20,as shown in phantom FIG. 8, serves as a darn for maintaining the ball ofmolten metal 38 on the terminal lug 12 after the molten metal has becomeproperly positioned on the terminal lug 12. If the clamp 20 did notoperate to remove the excess heat energy from the welding zone,destruction of the terminal lug 12 could result.

Referring to FIG. 8, the positioning of the lead wire 16 and theterminal lug 12 within the clamp 20 is shown. The clamp 20 is inelectrical contact with the lead wire 16 and holds the lead wire in anabutting position with the terminal lug 12 during the welding process.

Thus, it will be appreciated that the overheat principle utilized in thepresent invention in which excess heat energy is applied to the weldingzone allows the welding of the wire lead 16 to the terminal lug 12without any prior cleaning of the terminal lug. This is possible sincethe excess energy is effective to burn through the normally existingcontaminants on the terminal lug 12. Further, it is not necessary toaccurately position the lead wire 16 for welding since the excess energygenerated in the welding arc will be sufficient to melt the extra lengthof the lead wire. The excess energy generated in the welding arc doesnot damage the terminal lug 12 since the clamp 20 operates as a heatsink to protect the terminal lug being welded.

It has been discovered that the inert gas discharging from the electrode24 and traveling in a downward direction results in metal particles andother forms of soot being deposited on the resistor 10 and make itunsuitable for commercial useage. The conduit 82 discharges inert gasinto the welding zone in a direction which is preferably slightly upwardfrom a horizontal plane and combines with the gas discharged fromelectrode 24. The resultant inert gas flow directs the metal particlesand other soot away from the resistor 10 and prevents discoloration ofthe resistor.

At the end of the welding process, the ball 38 of molten metal islocated between the arc and the copper wire 16. Consequently, there isno deterioration in the strength of the wire since the electric arc doesnot strike the wire as it emerges from molten ball 38. Also, since thefull mass of the wire is retained, there is no reduction in thecross-sectional area of the wire, thereby retaining the originalstrength of the wire. The final area of the weld is proportional to thesize of molten ball 38, which in turn is a function of the length ofterminus portion 17 of wire 16 projecting beyond terminal lug 12. Theweld is further strengthened by the fact that there is no loss ofsurface area of the terminal lug 12.

The inert gas shield 28 (FIG. 1) prevents the joint from oxidizingduring welding. Also, wire clamp 20 acts as a heat sink for the leadwire 16 and prevents the discoloration of the wire 16 by keeping thetemperature of the wire at less than an oxidizing temperature.

As seen in FIG. 6, a portion 40 of the vitreous enamel coating ofresistor 10 extends partially along the vertical extent of terminal lug12. During welding, a portion of this coating may be melted and includedwithin molten ball 38. Also, enamel film, oxides and other contaminantspresent on the exposed portion of the terminal lug 12 may be included inthe molten ball 38. However, such substances, which are known tocontaminate other known welded and soldered joints, do not impede thequality of the the weld formed by my invention since the oxides andinorganic contaminants are lighter than the pool of material, and flowfrom the weld interface to the weld surface, where they remain. In thislocation, the contaminants do not affect the strength or electricalcharacteristics of the weld, and may remain in molten mass 38 withoutdetracting from the quality of the weld. All organic contaminants,meanwhile, va-

porize under the heat produced by the arc.

The ability of the weld joint of my invention to be accomplished withoutprior cleaning of the terminal lugs is a decided advantage over knowntechniques for attaching wire leads to electrical and electroniccomponents. When resistor 10, for example, emerges from the oven inwhich the vitreous enamel coat is baked, an enamel film covers theprotruding portion of each terminal lug, and part of the enamel coatitself may adhere to the upper portion of .the terminal lug. Using themethod of the present invention, the additional step of stripping theend of the terminal lug is eliminated, thus reducing the cost ofmanufacture.

FIG. 2 illustrates one form of apparatus which may be used to carry outthe process of the present invention. The apparatus comprises a supportbase 42 which is attached a vertically disposed cylinder 44,-. Shaft 46,which is connected to a piston movable in cylinder 44,

is capable of vertical movement, under the control of suitable cylinderactuating mechanisms, not shown. Attached to the uppermost portion ofshaft 46 is shaft 48 which moves vertically in vertical aperture 50disposed in support 52. Movement of shaft 48 om aperture 50 is limitedby stop pin 54, attached at one end to shaft 48, and vertically movablein slot 56 of support 52. Firmly affixed to the uppermost extent ofshaft 48 is L- member 58 having a screw threaded shaft member 60disposed in a suitably threaded slot. One end of shaft memeber 60comprises a portion 62 which has a diameter only slightly less than thatof the core of resistor 10, which is located on and held in place byshaft member 60,'as will be explained.

As'previously described, in connection with the diagramatie embodimentof FIG. 1, two wire clamps 20, 22, are suitably secured to base 42. Eachclamp comprises two movable, slotted guides which hold the wires duringwelding, and operate to release the lead wires when the weldingoperation is completed. Wire clamps 20 and 22 hold copper wires 16 and18, respectively, in place so that the terminus ends 17 of each copperwire 16, 18 extend beyond the terminal lugs 12 and 14 by a distance ofapproximately /a inch. By proper actuation of cylinder 44, resistor 10is positioned between clamps and 22 such that the upper tips of terminallugs 12 and 14 abut wires 16 and 18. However, the terminal lugs 12 and14 need not be in electrical contact with the wires 16 and 18,respectively, since welding current only passes from the tungsten tip 26of electrode 24 to the wires 16 and 18 during welding.

Copper wires 16 and 18 are supplied to clamps 20 and 22 from identicalconvetional wire straightening and feeding means 62 located on oppositesides of support base 42. Cut-off means 64, 66 are disposed between wirefeed mechanisms 62 and clamps 20, 22. Cut-off means 64, 66 may belaterally positioned along support base 42 to alter the length of thelead supplied with the resistor.

Rigidly affixed to support base 42 and extending vertically therefrom iselectrode support 68 to which electrode 24 is pivotally mounted aboutpin 70. Tungsten tip 26 is movable from a position adjacent the terminusportion 17 of wire 16 to a position adjacent the terminus portion 17 ofwire 18. The electrode 24 is maintained in a pivotal position relativeto support 68 such that tungsten tip 26 may be positioned approximatelyl/32 inch above the terminus portion 17 of wires 16 and 18, andapproximately 1/16 inch from the tips of each wire. Electrode 24 isconnected to a source of electrical power and inert gas, as previouslydescribed (FIG. 1).

The operation of the welding apparatus of FIG. 2 is as follows: Shaft 46is withdrawn into cylinder 44 by suitable control means, which in turnlowers threaded shaft member 60 as shaft 48 drops vertically in aperture50. When pin S4reaches the lowermost limit of slot 56, shaft 48 stops,and shaft member 60 is held in place. An operator places a vitreousenameled resistor 10 over shaft member 60, laterally locating theresistor by means of collar 72, and actuates cylinder 44 to raiseresistor 10 into the position shown in FIG. 2. When lugs 12 and 14 reachand come into contact with wires 16 and 18, resistor 10 stops and isproperly located.

Feeder mechanisms 62 provide a supply of wire to clamps 20 and 22, whichholds the wires in .position atop terminal lugs 12 and 14 of resistor10. As stated previously, approximately /8 inch of wire extends beyondeach terminal lug. Electrode 24 is swung into position whereby tungstentip 26 is located above the terminus portion of either wire 16 or 18. Itis important to note here that tungsten tip 26 is not located directlyover terminal lug 14, but lies above a point approximately midway of theterminus portion 17 of the wire 16, 18 extending beyond terminal lug 12,14.

The welding machine 22 (FIG. 1) is started and an electric arc is struckbetween tungsten tip 26 and wire 16 or 18, and a weld is formed inaccordance with the procedure described,referring to FIGS. 1 and 6.After this first weld is formed, electrode 24 is swung into positionsuch that tungsten tip 26 is located above the terminus portion 17 ofthe remaining unattached wire. Another arc is struck, and the weldingprocess is repeated.

With the wires 16 and 18 now firmly attached to lugs 12 and 14 ofresistor 10, cut-off means 64 and 66 are actuated to serve the copperwires at a point whereby the desired length of the wire leads isobtained. The cylinder 44 is actuated to lower shaft 46 and resistor 10and the copper wire leads which were formed by the welding operation arereleased by the clamps 20 and 22. As the resistor drops below the workstation, it is removed from shaft 60. A new resistor 10 is placed overshaft 60, additional wire 16, 18 is moved into place in the clamps 20and 22, and the above-described steps are repeated. Alternatively, apair of welding electrodes could be utilized to perform the welding ofthe wires 16 and 18. This would permit both wires 16 and 18 to be weldedto the lugs 12 and 14 simultaneously. Also, the apparatus shown in FIG.2 could be placed on a rotatable work table and the table could berotated to move the apparatus and associated resistor 10 from onw workstation to a second work station. The first work station could have awelding electrode 24 and associated gas supply structure for welding oneof the wires 16 and 18 while the second work station could have anelectrode similar-to the electrode 24 as 'well as an associated gassupply to weld the other one of the wires 16 and 18.

The welding process described is not limited to the particular weldconfiguration illustrated in FIGS. 1 and 6. The copper lead wires 16 and18 may assume different locations relative to the terminal lugs 12 and1.4 to suit special requirements. In FIG. 3, for example, the wire 16 isplaced across the top edge of terminal lug 12 so that the axis of wire16 is perpendicular to the plane of the terminal lug 12 of resistor 10.The welding of wire 16 to the terminal lug 12 in the embodiment of FIG.3 is accomplished in the same manner described in conjunction with theembodiment of FIG, 1. The tungsten tip 26 of electrode 24 is placedmidway between and slightly above terminus portion 17 of copper wire 17.An electric arc is struck between tungsten tip 26 and terminus portion1?, creating a source of heat which'melts the copper wire. As the wiremelts, it forms a ball of molten metal 38, as previously described,which travels along the wire until it coalesces with the flat surface ofterminal lug 12, at which time the arc is extinguished.

It has been found that the welding process of the embodiment of FIG. 3is particularly suited to welding flexible leads such as made frombraided or stranded copper wire to terminal lugs of resistors or otherelectrical or electronic components or elements. A flexible lead by itsvery nature is difficult to pre-form and hold in position for rapidmechanical assembly. Also, when soldering a flexible lead, the leadloses its flexibility for a considerable distance from the joint becauseof the capillary action of the stranded wires. The arc welding processof the present invention enables flexible copper leads to be welded to awide variety of metals or other elements with virtually no loss offlexibility or strength.

further embodimentshowing an applicat io h ofthe present invention isshown in FIG. 4, where the copper wire 16 is maintained under pressureagainst the lateral face of terminal lug 12. Tungsten tip 26 ofelectrode 24 is placed near the junction of the wire and terminal, andan electric arc is struck at the junction. As'the heat of'the arc meltswire 16, constant pressure on wire 16 forces it to feed into thejunction, forming a molten mass of copper around the junction. When thearc is distinguished, the copper solidifies and coalesces with theterminal lug material, and forms a flllet of material 38' around thewire at the junction point.

An additional embodiment of the present invention is illustrated in FIG.5, where the terminal lug 12 com prises an aperture 80 centrallydisposed therethrough. Copper lead wire 16 projects through aperture 80such that terminus portion 17 or wire 16 extends a distance ofapproximately /8 inch beyond terminus lug 12. Electrode 24 is positionedsuch that tungsten tip 26 is located slightly above the midpoint ofterminus portion 17. To accomplish the weld, an arc is struck betweentungsten tip 26 and terminus portion 17 of wire 16, and the heatproduced by the arc melts the wire back to the face of terminal lug 12.A combinationball and fillet of molten copper 38" is formed, whichcoalesces with the material of terminal lug 12 around aperture 80, andadheres wire 16 firmly to the terminal lug.

In the embodiments illustrated in FIGS. 3, 4, and 5, the terminal lug 12may sometimes be made of a relatively thin material. To prevent the heatof the welding are from burning the terminal lug, a chill bar may beattached to the lug. This chill bar may comprise a clamp or other solidmetal object which is placed in contact with the lug and absorbs ordraws away most of the heat of the arc during welding; As most of theheat is absorbed by the chill bar the terminal lug is prevented fromreaching its melting point, except in the area directly adjacent themolten ball 38 where coalescing occurs.

To achieve a strong and electrically efficient weld when employing thesteps of the methods of the embodiments of FIGS. 1 and 3-5, the terminusportion 17 of copper wire 16 must extend beyond terminus 12 by a smalldistance, usually /a inch, and the are placed adjacent the terminusportion. FIG. 7 illustrates the damage which will result if the copperwire 16 is placed atop terminal lug 12 with the end of the wire adjacentthe vertical edge of the lug 12 with no portion of the wire extendingbeyond the terminal lug. When so positioned, the heat of the welding arewill melt a portion of the terminal lu'g itself, as shown in FIG. 7, andprevent the fomiation of the ball of molten metal 38(FIG.

6) which provides strength and quality to the weld with no loss ofsurface area of the terminal lug.

In each of the embodiments of the present invention, heat for welding isgenerated by an electric arc generated from the tungsten tip 26 ofelectrode 24 to the lead wire 16 or 18. Clamps 20 and 22, and groundwires 21 and 23 complete a path for the conduction of the electriccurrent. No electrical connection need be made to the terminals 12, 14,as opposed to resistance welding where electrical connections must bemade to both the wire and the terminal. Further, the present in vention,with the exception of the embodiment illustrated in FIG. 4, relates to awelding method and apparatus whereby one part to be welded is merely incontact with the other part, and no pressure is applied. This differswith previously known welding techniques where there must be some degreeof pressure between parts for forming a proper junction. A furtheradvantage of the present invention with the exception of the embodimentdisclosed in FIG. 4, is that the copper wire and terminal lug remainstationary during welding, while some known welding techniques'requirethat the wire must be moved, under pressure, into the junction. W TheEdit welding technique of the present invention, illustrated in FIG. 4,has decided advantages over known butt or percussion welding methods. Inusual percussion welding methods, the electrical current from the arcmust pass through the terminal lug and the wire, and a connection mustbe made to the terminal. In the case of small terminal lugs, as arepresent in most electrical or electronic components, this presents asevere limitation on the configuration of weld which can be used. Noshielding gas is used in percussion welding, requiring that the junctionmust be free of contaminants. This results in an extra production stepwhich is eliminated in the present invention. Using my butt weldingprocess (FIG. 4), electrical current need only pass through the wire,and not the terminal, which is usually small and difficult to connect toan electrical conductor for welding. Also, as previously explained, theterminal need not be cleaned prior to welding.

My invention may-also utilize the metal inert gas welding technique (MIGwelding) to produce an electrical or electronic component having acopper wire lead welded thereto. Metal inert gas welding is similar totungsten inert gas welding (TIG welding) except that the electrodecomprises a filler metal (copper in'the present case) which is consumedas the electric arc melts the electrode. Using MIG welding methods inthe butt welding process of FIG. 4, the wire 16 becomes the consumableelectrode. In this application, electrical connections must be made toboth the wire and the terminal! After striking the arc, the wire is fedinto the junction at a rate greater than it is consumed, therebyextinguishing itself and coalescing.

The foregoing embodiments are exemplary of the process, product andapparatus of the disclosed invention, and may be used as a model forconstructing the invention. However, many variations of the discloseddevice may be made without departing from the spirit and scope of theinvention as defined in the following claims.

What is claimed is:

' of an electronic component, said terminal lug having v 13 contaminantsthereon, comprising the steps of:

positioning the lead wire in an abutting relationship with the terminallug of the electronic component, an end portion of the lead wireextending beyond said terminal lug a predetermined amount;

shielding a welding zone formed by the lead wire and the terminal lug ofthe electronic component with an inert gas;

generating a welding are between the end portion of the lead wire and awelding electrode to form a ball of molten material on the lead wire;

maintaining the welding are for a period substantially greater than theperiod necessary to form a coalesced mass of molten material from thelead wire and the terminal lug of the electronic component in order toproduce an excess of heat energy in the welding zone and burn away thecontaminants on the terminal lug; and carrying away from the lead wireand the terminal lug of the electronic component excess heat energyproduced in the welding zone. I 2. The method of Claim 1 furtherincluding the step forming a dam on the lead wire and the terminal lugof the electronic component to contain the coalesced mass of moltenmaterial in position on the terminal lug of the electronic component.

3. The method of claim 2 wherein the step of shielding the welding zonewith inert gas includes the steps of:

discharging inert gas downward from the electorde to the welding zoneand discharging inert gas in a substantially horizontal direction intosaid welding zone whereby the resultant flow of inert gas exiting thewelding zone is directed away from the electronic component beingwelded.

4. The method of claim 3 wherein the welding arc is nanitaifiararaperiod'of time approximately twice positioning a clamp on the lead wireand the terminal lug of the electronic component, said clamp being inelectrical contact with the lead wire; shielding a welding zone formedby the lead wire and the terminal lug of the electronic component withan inert gas; generating a welding are between the end portion of thelead wire and the welding electrode to form a molten ball of materialfrom said lead wire, said molten ball of material heating the terminallug; maintaining the welding are for a period of time substantiallygreater than the period of time necessary to form a mass of moltenmaterial from the lead wire and the terminal lug of the electroniccomponent in order to produce excess heat energy in the welding zone andburn away the contaminants on the terminal lug; and carrying away fromthe lead wire and the terminal lug of the electronic component throughsaid clamp the excess heat energy formed in the welding zone. 6. Themethod of claim 4 wherein the welding arc is maintained for a period oftime approximatelytwice the period of time necessary for forming themass of molten material from the lead wire and the terminal lug.

Patent No HARRY CHANOWITZ lnventor(s) Dnted i l 'Ch 5 Column line 25Column line 28- Column line 30 Column line 7 Column line Column line 13Column 10, line 16 Column 10, line 63 Signed and sealed this (SEAL)Attest:

moor M. GIBSON JR. Attesting Officer FORM PO-105O (IO-69) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

"he" should read -the-.

"publication" should be --application.

"method" should read methods-.

"1.980 1 should read --1, 980F-- "25" should read 24.

"17" should read -l6-'-.

17th day of September 1974.

C. MARSHALL DANN Commissioner of Patents 'USCOMM-DC 6O376-P69 u.s.GOVERNMENT PRINTING OFFICE Iss9 0-366-334,

1. A method of welding a lead wire to a terminal lug of an electroniccomponent, said terminal lug having contaminants thereon, comprising thesteps of: positioning the lead wire in an abutting relationship with theterminal lug of the electronic component, an end portion of the leadwire extending beyond said terminal lug a predetermined amount;shielding a welding zone formed by the lead wire and the terminal lug ofthe electronic component with an inert gas; generating a welding arcbetween the end portion of the lead wire and a welding electrode to forma ball of molten material on the lead wire; maintaining the welding arcfor a period substantially greater than the period necessary to form acoalesced mass of molten material from the lead wire and the terminallug of the electronic component in order to produce an excess of heatenergy in the welding zone and burn away the contaminants on theterminal lug; and carrying away from the lead wire and the terminal lugof the electronic component excess heat energy produced in the weldingzone.
 2. The method of Claim 1 further including the step of: forming adam on the lead wire and the terminal lug of the electronic component tocontain the coalesced mass of molten material in position on theterminal lug of the electronic componEnt.
 3. The method of claim 2wherein the step of shielding the welding zone with inert gas includesthe steps of: discharging inert gas downward from the electorde to thewelding zone and discharging inert gas in a substantially horizontaldirection into said welding zone whereby the resultant flow of inert gasexiting the welding zone is directed away from the electronic componentbeing welded.
 4. The method of claim 3 wherein the welding arc ismaintained for a period of time approximately twice the period of timenecessary for forming the coalesced mass of molten material from thelead wire and the terminal lug.
 5. A method of welding a lead wire tothe terminal lug of an electronic component such as a resistor, saidterminal lug having contaminants thereon, comprising the steps of:positioning the terminal lug of the electronic component in an abuttingrelationship with the lead wire, and end portion of the lead wireextending beyond the terminal lug of the electronic component apredetermined amount; positioning a clamp on the lead wire and theterminal lug of the electronic component, said clamp being in electricalcontact with the lead wire; shielding a welding zone formed by the leadwire and the terminal lug of the electronic component with an inert gas;generating a welding arc between the end portion of the lead wire andthe welding electrode to form a molten ball of material from said leadwire, said molten ball of material heating the terminal lug; maintainingthe welding arc for a period of time substantially greater than theperiod of time necessary to form a mass of molten material from the leadwire and the terminal lug of the electronic component in order toproduce excess heat energy in the welding zone and burn away thecontaminants on the terminal lug; and carrying away from the lead wireand the terminal lug of the electronic component through said clamp theexcess heat energy formed in the welding zone.
 6. The method of claim 4wherein the welding arc is maintained for a period of time approximatelytwice the period of time necessary for forming the mass of moltenmaterial from the lead wire and the terminal lug.